1. Field of the Invention
The present invention relates to liquid crystal displays, and in particular to a transflective liquid crystal display having uniform openings in different color filter units of a color filter layer and corresponding reflective electrodes with different areas.
2. General Background
Liquid crystal displays (LCDs) generally have advantages of lightness in weight, a thin shape, flexible sizing, and low power consumption. For these reasons, LCDs are widely used in portable products such as laptops, personal digital assistants, mobile phones, and so on. Conventional transmissive LCD devices require an accompanying backlight to provide the light needed to illuminate liquid crystal of the LCD, so that the LCD can provide images for display. Typically, an LCD together with a backlight module is installed in a portable product. However, in these kinds of portable products or devices, it is desired to reduce power consumption of the backlight modules and increase a contrast ratio of the LCD in direct light. As a result, a transflective type of LCD was developed.
FIG. 5 is a schematic, side cross-sectional view of part of a conventional transflective LCD. The transflective LCD 100 includes an LCD panel (not labeled) and a backlight module 140. The LCD panel includes a first substrate 110, a second substrate 130, and a liquid crystal layer 120 interposed between the first and second substrates 110, 130. The backlight module 140 is disposed adjacent to the second substrate 130.
The first substrate 110 includes a first glass substrate 111 having a color filter layer 112 and a common electrode layer 116 sequentially formed on an inner face thereof. The color filter layer 112 includes a plurality of red filter units 113, green filter units 114, and blue filter units 115 arranged in a matrix. For simplicity, FIG. 5 only shows one of the red filter units 113, one of the green filter units 114, and one of the blue filter units 115. Each of the red filter units 113, green filter units 114, and blue filter units 115 has an opening 119 through the color filter layer 112.
The second substrate 130 includes a second glass substrate 131 having an insulation layer 132 and a conductive layer (not labeled) sequentially formed on an inner face thereof. The conductive layer is divided into a plurality of sub-pixel units 133. The sub-pixel units 133 are arranged in a matrix corresponding to the matrix of the red filter units 113, the green filter units 114, and the blue filter units 115. Each of the sub-pixel units 133 includes a transmissive electrode 134 and a reflective electrode 135. The transmissive electrode 134 of each sub-pixel unit 133 defines a vertical transmissive region of the LCD panel thereat. The reflective electrode 135 of each sub-pixel unit 133 defines a vertical reflective region of the LCD panel thereat.
When the transflective LCD 100 functions normally, light provided by a backlight module (not shown) below the second substrate 130 sequentially passes through the second glass substrate 131, the insulation layer 132, the transmissive electrodes 134, the liquid crystal layer 120, the common electrode layer 116, the color filter layer 112, and the first glass substrate 111. Thus the backlight module provides light for displaying of images by the transflective LCD 100. Simultaneously, light provided by an external light source (such as sunshine or an indoor light, not shown) above the first substrate 110 sequentially passes through the first glass substrate 111, the color filter layer 112, the common electrode layer 116, and the liquid crystal layer 120. Some of this light is then reflected by the reflective electrodes 135 of the sub-pixel units 133. The reflective light passes back through the liquid crystal layer 120, the common electrode layer 116, the color filter layer 112, and the first glass substrate 111, and thereby provides additional light for displaying of images by the transflective LCD 100.
The openings 119 formed in each of the red filter units 113, the green filter units 114, and the blue filter units 115 of the transflective LCD 100 correspond to the locations of the reflective regions defined by the reflective electrodes 135 of the sub-pixel units 133. Therefore, part of the outgoing reflective light directly passes through the openings 119 without passing through the colored parts of the color filter units 113, 114, 115 of the color filter layer 112. This can increase the luminance of the reflective regions of the transflective LCD 100.
FIG. 6 is a schematic, top plan view of a part of the color filter layer 112 corresponding to the part thereof shown in FIG. 5. Referring to FIGS. 5 and 6, the areas of the openings 119 of the three different color filter units 113, 114, 115 are different. That is, the openings 119 of the green filter units 114 are larger than the openings 119 of the red filter units 113, and the openings 119 of the red filter units 113 are larger than the openings 119 of the blue filter units 115. The reflective light passing through the color filter layer 112 includes two portions. One portion is the light passing through the colored parts of the color filter units 113, 114, 115, and the other portion is the light directly passing through the openings 119 of the color filter units 113, 114, 115. The luminance in the reflective regions can be enhanced because white light directly passing through the openings 119 is not absorbed at all by the colored parts of the color filter units 113, 114, 115.
The reflective regions corresponding to the green filter units 114 are brighter than those corresponding to the red filter units 113 and the blue filter units 115, because the openings 119 of the green filter units 114 are larger than the openings 119 of the red filter units 113 and the blue filter units 115. Similarly, the reflective regions corresponding to the red filter units 113 are brighter than those corresponding to the blue filter units 115, because the openings 119 of the red filter units 113 are larger than the openings 119 of the blue filter units 115. Thus the chromaticity of the reflective light meets the requirements of CIE chromaticity coordinates for display devices, which requires that the luminance of green light is the largest, the luminance of red light is the second largest, and the luminance of blue light is the smallest.
During manufacturing of the color filter layer 112 of the transflective LCD 100, the different color filter units 113, 114, 115 are formed separately and sequentially. However, the areas of the openings 119 of the red filter units 113, the green filter units 114, and the blue filter units 115 are different. Therefore, the manufacturing process requires three different photolithography masks with three different opening patterns for the different color filter units 113, 114, 115. The cost of fabrication of all the masks is correspondingly high. Hence, there is a need for a simpler and inexpensive configuration for a transflective LCD which requires fewer photo masks in the manufacturing process.